Wikipedia claims (not very current claims though) that terminator seeds are not commercially available?
They are different than the common case of infertile hybrids, which have good reason to exist and the infertility (IIUIC, not a botanist) is a side effect.
There was an old patent about making generations completely infertile, but yes, never used. Bayer's corn seeds are optimized enough that, while the next generation grows just fine, the yield loss makes it not worthwhile over just buying new seed.
Its been that way for a lot of crops for almost a century at this point. This phenomenon is called hybrid vigor. Many things we grow are clonally propagated at this point to maintain these hybrid genetics.
They are different than the common case of infertile hybrids, which have good reason to exist and the infertility (IIUIC, not a botanist) is a side effect.